The proposed research is aimed at completing a convergent, stereoselective total synthesis of a recently characterized glycoslyphosphatidylinositol (GPI)-anchoring inhibitor YW3548. YW3548 consists of unusual tricarbocyclic sesterterpenoid delta-lactone framework and is a very potent inhibitor of GPI synthesis in eukaryotic cells. The proposed convergent synthesis will feature a sequential intermolecular carbonyl addition to a vinyl carbanion followed by an intramolecular nucleophile acyl substitution mediated by diiododsamarium to form the functionalized eight-membered carbocyclic ring B. This approach is unique in that it produces alkenyl, oxo and diol substituents, which will provide handles for synthetic elaboration of the generated eight-membered ring. The strategies for formation of the molecules involved in the sequenced reaction are described along with a route to the completion of YW3548.